Printing mechanism



Aug. 3, 1943. R. B. JoHNsoN PRINTING MECHANISM '7 Sheets-Sheet l Filed Deo. 27, 1940 y INVENTOR ATTORNEY ,Allg 3, 1943. R. B. .JOHNSON 2,325,958

PRINTING MECHANISM Filed Dec. 27, 1940 7 Sheets-Sheet 2 358 32% $7 l l II "-327 136- 142 @148 naw 48 vd@ J4? 104 o z L 143 118 105 1 4 1 3 169 H43 2 "[7 173 1' J '75 163 123 e 171 37 IIIIHHI Imm' 1 2 L/ 1 s I 4 122 j INQTOR ATTORNEY B. .JOHNSON 2,325,958

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P INT ING MECHANI SM Aug. 3, 1943, R. B. JOHNSON PRINTING MECHANISM 7 :fleets-Sheet '7 Filed Dec. 27

'ATTRNEY Patented Aug. 3, 1943 PRINTING MECHANISRI Reynold B. Johnson, Binghamton, N. Y., assigner to International Business Machines Corporation, New York, N. Y., a corporation of New York Application December 27, 1940, Serial No. 371,867

(Cl. 23S-61.3)

8 Claims.

The present invention relates to the printing mechanism of a machine for electrically grading response sheets upon which an examinee has designated response by means of pencil marks. The machine constitutes improvements over the machine shown in my Patent No. 2,113,620, granted April 12, 1938.

The functioning of the machine depends on the fact that a soit lead pencil or special ink mark is electrically conductive and that the amount of current flowing through each pencil or ink mark may be Controlled and kept to a uniform unit, whether the mark is very heavy or relatively light.

When the response sheet is inserted in the machine, it is pressed against a contact plate containing 750 sets of sensing blades corresponding to the 750 response positions on the response sheet. These sets of sensing blades consist eachk of ve small parallel metal blades which are connected alternately to the positive and negative sides of the circuit. Whenever a pencil mark i`s pressed against one of the sets of sensing blades,

it closes the electric gap between the positive and negative blades and a unit of current flows through the circuit.

The machine distinguishes between right and wrong answers by means of a perforatedv key sheet which automatically divides the sensing blade units intotwo groups, the "right and the wrong From this division, two meter circuits result, one carrying the aggregate of the units of current from the correct responses and the other carrying the aggregate of the units of current from the incorrect responses.

In my copending applicationA Serial No. 214,- 922, filed June 2l, 1938, now issued as Patent No. 2,275,590, dated March 10, 1942, I provide a large milliameter and switching devices through whichright responses on the answer sheet being The score' pressed against the sensing blades. indicated on the meter is recorded by the operator -on the exposed margin ofA the response sheet or on a separateV record sheet or the operator may call the score to a recording clerk.

Ii the score is in'v terms of the number wrong,

the current from the wrongs circuit is routed2 through the meter which' indiciates to the operator the numb'erwrong.

If the score .is in terms of rights minus Wrongsf the wrongs circuit is connected to the opposite side of the meterv from the rights" circuit, so that the meter reading is' the difierence between the two currents, thus registering the rights minus the the wrongs According to the present invention, there is employed instead of an indicating meter a printing mechanism having a pair of printing wheels located adjacent to the examination sheet from which wheels the score is printed upon the sheet. The wheels arranged to rotate from a zero position through all the possible scoring values up to the maximum and, when the value corresponding to the score is reached, a printing hammer is tripped to effect printing. The printing mechanism has associated with it a number of resistors which are cut into a circuit opposing the circuits 'through the sensed marks and, when the current resulting from the resistors introduced in circuit by the examinees response is balanced by the resistors introduced by the printing mechanism, this condition of balance is detected by an impulse transformer and a thyratron tube. The thyratron tube causes the print hammer to strike the rotating type wheels, recording the position of balance which is then directly proportional to the score of the examinees answer sheet.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which" disclose, by way of example, the principle of the invention the best mode, which has been contemplate-l', cf applying that principle.

In the drawings:

Fig. l is a iront View of the machine with the casing partially broken away to show the interior construction. .Y

Fig. 2 is a sectional view taken transversely across the machine.

Fig. 3v is a diagrammatic showing of partv of the circuit arrangement.

Fig. 4 is a view showing the control circuit for the driving motor.

Figs. 5 and 5a.'.plaeed side by side in the order named, constitute a wiring diagram of the electric circuits of the machine.

Fig. 6 is an enlarged outside view oi the printing mechanism.

Fig. '7 is a section taken on lines l-l of Fig. 6.

Fig. 8 is a section taken on lines 8 3 of Fig. 6'.

Fig. 9 is a section taken on lines 9-5 of Fig. 6l

Fig. l0 is a detail of the printing hammer and the related mechanism.

y looking from the left in Fig. 6.

of its restoring spring Y 'the disk ser.

Fig. ll is a detail of the printing mechanismL Fig. l2 is a section taken on lines i-i or Fig. 1l.

I Reference to Patent No. 2,275,597is Ymede for disclosure of the detailed construction operation of the Ymachine to which the present ivention is applied. Sufficient of such machine -is shown in Figs. l and 2 to indicate where the printing mechanism of the invention is located,

and the manner in which electrical coordinatie Fig. l and the details thereof are shown Yin Figs. 6 to l2 inclusive. The mechanism of the printing unit is driven by motor Ml which receives current upon closure of a pair of contacts 398 Xsee Fig. d). These contacts 38d shown in Figs. 6 and 'Zywhere they are closed by a inanually operated key Shi. On the shaft of 'motor MisV a pinion 382 meshing with a gear 3 3 which is freely mounted on the shaft integral with gear 3&3 is a ratchet 335 in the planeof which lies a spring-pressed clutching dog 35 which is pivoted to a disk 3Q? secured to the shaft 3de. Normally, ie parts occupy the position shown in Fig. 7.

When key 36S is depressed the atoll Y 2h58; disk is released as is also the dog 365, which latter is then engaged by ratchet' for rotation. Key 3M is held in its depressed position by engagement-J of its eX- tension 389 with the periphery of the disk 313i'. Just before the completion of the revolution of shaft 3M, a disk Si@ and a toothed member lll secured thereon will be in the position ion SI2 and through it rotates a gear Si@ one step or tooth, so that shaft l upon which pinion 3l3 is secured, will be advanced one tooth or a tenth of a revolution, inasmuch as pinion 3 E3 SI2 are provided with ten teeth. The pinion 3i3 isnormally held in position by a detent pin' 3|5 (see also Fig. 6) which is carried by a verticallysildablebar BEE whose upper end carries a roller 3l? cooperating with the disk The timing is such that, as the toothed member 3H rocks pinion Sli, the roller 353 is in a depression in the periphery of disk 3S@ so that thedetent 3l5 is withdrawn downwardly to permit rotation of pinion SH3, after which disk El@ again ele-A vates the detent to hold shaft Bill in its advanced position. Y

At the extremity of shaft @lil is a disk (Fig. 7) whichat this time is free of the eX- tension Sill on key inasmuch as the key is held in its depressed position at this time-by Disk @i8 upon rotation will serve to maintainv the key depressed even though extension Still is freed at the completion of a revolution of shaft 3il. As a result, shaft continues through a second revolution, near the end of wl'nch shaft Sid is again advanced a 'tenthof a revolution in the saine manner. YThis continues until shaft Sii has made ten revolutions when shaft Slfl will have made one complete revolution. `it such time both disks Stil and 353 will be in the relative positions shown in Fig; if so that spring 368 will return key 363i upwardly and shown inY Fig. 8. The member Ell engages an idler pin- Y tremity of which is secured a type wheel (see Y also Fig. 1l). The shaft Sid also has a beveled gear 326 secured Ythereto which meshes with a beveled gear freely rotatable vvon shaft and connected to a sleeve which carriesa type wheel 321. It will thus be apparent that,

when motor Ml is energized, it continues running until the type wheel, 323 has ten rev- Volutions and type wheel'32'l has made one rev- `olution to successively present the numbers l to 9i! `into printing position opposite printing hammer 328.

Hammer 32e is pivoted at sie (Fig. 12) and has connected thereto at 373B a member which is normally in the position shown in l2 where it is held by. a spring 32 against a pin 333 (see also. Figsll and 10)'. Mounted on Vshaft lt is a cam wheel 334 (Figs. 6 and 9). which oscillates arbell crank follower arm 335 ten times'for'each revolution of shaft Sll. The lower end of this follower has a lateral eXtension'-G which rocks back and forth idly.V

The pin 333 against `which the member 533i Vis spring( biased is carried by the armature leverl of a magnet 338 (see Fig. l0), so that when the. magnet is energized the lever 33t is rocked from the positionshown in Fig. 12 to' that shown ii Fig.` 10 andan upward extension of member 33E is brought into the path of the oscillating projection 336, which projection will engage the `extension 339 ward the left as viewed in Fig. i0, whereby the hammer 328 will be rapidly Vrocked against the printing wheels to take an impression therefrom. TheV timing of the parts is such that wheel 32? is stationary at the time the hammer is tripped, whereaswheel 323' is in motion with one of the digits thereof in printing position. As will be 'explained later in connection with the'circuit diagram, the time of energisation of magnet 338 will determine the Value ofl the amo-unt to be printed from the printing wheels, thatfis, as thewheels bers according to the time rat which magnet 335' is energized. Lying abovejthe pivoted pin Stil is aspring pressed pivoted latch Se@ (see Fig. il) which, when the hammer is rocked from the po sition of Fig. l1 to that of Fig. 10,'will drop down behind the pin 33S to hold the hammer against restoration andvagainst further operation by the oscillating projection 336. e

Near the end'of the revolution of shaft 3 it, the magnet Sill is energized to rock latch 36S out of engagement with pin 338, allowing the hammer to be restored bythe spring 332. In Fig. lZthere is indicated the inking ribbon 315,12. The detailed feeding mechanism is not shown as such devices are well known in the art.

Secured to shaft 3M isa group `of nine'camsv and move member 33! rapidly to-V v `group of nine cams*` generally designated 3l5 which serve to control contacts 346 which also serve to close the contacts 346in succession and to open them concurrently at the end of a revolution of shaft 314. Since shaft 314 makes but a single revolution during an operation of the printing mechanism, there will be but a single closure oi each of the contacts 345. rThe timing is such that the contacts 344 first close in succession with all the contacts 346 open, then the contacts 344 close in succession a second time with the iirst contact 346 closed. The next operation of the contacts 344 takes place with the rst and second contacts 346 closed and so on.

On shaft 354 are three additional contact operating cams designated 34'1, 343 and 343 (Fig. 5). These cams control contacts designated 350, 351 and 352 respectively (see Fig. 5). There is also a cam 353 on shaft 304 which controls a pair of contacts 354 (Fig. 5). On shaft 314 is an additional cam 355 controlling a pair oi contacts 356. The functions of these several cam controlled contacts will be more fully explained in connection with the circuit diagram (Fig. 5).

The mechanism of the printing unit is supported on a channel 35'1 (Figs. 6 and 12). This channel is mounted on a pair of cross rods 35B secured to a fixed part of the machine. Between the two cross iods is a pair of spring pressed detenting plungers 359 which cooperate with notches 365 in the rods, so that thek entire printing unit may be located in one of several positions. The unit is mounted on the machine as shown in Figs. l and 6, so that the printing wheels lie adjacent to the examination sheet R when the latter is inserted in the guide chute 9?. The latter is cut out as indicated to provide for operation of the printing hammer The printing unit is made shiftable so that the numerals may be printed in any of several positions on the examination sheet.

From Figs. 6 to l2 it is seen that the printing unit in its mechanical structure comprises generally a motor Mi' and a direct drive connection from the motor to a pair of printing wheels. With the motor in operation, the wheels turn so that the tens order wheel 321 makes one revolution in ten steps while the units order wheel 323 makes ten revolutions, one for eachI step of the tens order wheel, so that the numbers 1 to 99 are presented in succession to a printing position opposite hammer 328. Once the motor Mi is put in operation, it continues to run until all the numbers 1 to 99 have been presented and then stops. During its operation, various cams 343, 345, 341, 348, etc., function to control circuit connections as will be explained in connection with the circuit diagram to energize the printing magnet 338. The printing hammer is normally idle and lies spaced away from the printing wheels (Fig. 12). By means of cam 334 (Fig. 9) arm 335 is rapidly and repeatedly oscillated, once for each of the presented numbers 'i to 99, such oscillation being ineffective until magnet 33S is energized at the time a particular number is at the printing position. Thereupon, the hammer 328 is coupled through the intermediate lever 331v to the arm 335, so that the latter engages and forcibly rocks the hammer toward the wheels, the stroke being such that the positive action carries the hammer just up to the Wheels and the inertia of the hammer completes the impression, the rebound and spring 32?. ythereafter bringing and holding the hammer in the position of Fig. 10 slightly away from the wheels so as not to interfere with their continued rotation. Just before the motor MI is deenergized, magnet 341 is energized to release the hammer for return to its positionof Fig. 12 in readiness to be tripped during a subsequent operation of the unit.

Circuit diagraml vEach of the resistors 69 shown in Fig. 5a and each of the resistors 361 in Fig. 5 has a resistance of 2 megohms. Each of the resistors 362 in-Fig. 5 has a resistance of 200,300 ohms. Potentiometers designated 201 and 2&2 have a value of 50 ohms, andthe battery designated 131 may have a value of 90 volts. In Fig. 5 the structure of the several switches in shown diagrammatically and the manner in which they are identiiied will be briefly set forth at this time.

Each of the knobs of formula switches Illia, 18Go and lc (Fig. 2) of Patent 2,275,590 is connected to a pair of switch blades F1 and F2 of which the former may connect a series of segments Fia designated R-W, W, R, A and B, and the iatter may connect a series of similar segments F'Za similarly designated. As the three switches are identical in structure, the corresponding parts are given similar reference characters and in tracing the circuits they will be distinguished as, for exanipie the Fi blade of formula switch A. The master control switch Iitl has three blades designated C1, C2, and C3 for engagement with segments identified as Cia-Cim respectively.

The tivo potentiometer resistances ii and E32 form two arms of a Wheatstcne bridge, Awhile the resistors 69 form a third arm, and the resistors 351 and 362 form the fourth arm. The bridge arrangement is diagrammatically represented in Fig. 3 in connection with which the principle of operation may be briefly set forth. When an examination sheet is sensed, a number of resistors 59 are connected in parallel into an arm of the bridge as indicated by the four resistances designated right When the printing mechanism is placed in operation, the resistors 361 under control of the cams 343 and related contacts 344 (see Fig. 5) are successively connected in parallel into the other arm of the bridge. As long as the bridge is unbalanced, current flows through the diagonal to energize a coil 363. As will be explained, the passage'of current through this coil will normally prevent tripping of the printing hammer.

When equilibrium of the bridge is attained, current fails to pass through coil 3,53 and this condition will be detected and other circuits called into operation to energize the printing magnet, so that the printing hammer will print on the examination sheet a number corresponding to the value of the resistors Sti required to balance the bridge. Where the marks sensed are classified as right or Wrong responses, a number of resistors 69 representing right answers is connected in the arm as explained and a number of resistors 53 corresponding to the number of Wrong marks is connected into the opposite arm as represented, so that upon the sensing of the examination sheet the bridge is unbalanced in accordance with the difference between the number of right and wrong responses. Under such conditions the number of print unit resistors 351 connected into the related arm to balance the bridge will represent the difference between the two classes of marks, provided there are more right marks than Wrong marks.

Referring to Fig. 5, the positive side 0f battery 181 is connected vto the master control switch blade Cnwhich may be on either the A, B, 011C segment Ca. With the switches in the A posi'- tion, current flowsY to the A potentiometer 20j, through wire 2li), and some ofV it flows back thro-ugh the resistances 232, wire 293, VVto the A position segment Cja, switch C2 to the negative side of battery. From the connection be-V tween the two resistors 26|, 22 .thereis a connection Zi to theV A segment Cla` of switch Cl, thence torcontact' 35E?,VV a pair of contact 354 operated by a key 3t5, the winding 363, to acon- Vnecting point 366. Here the connection branches mark to sensing .blade d and tothe high resistor 5t corresponding to the position in which a mark is present. According to the position of the key set pin i6, the current will follow from the resistor 59 to either the blade structure 92 or the blade structure Q3, depending on whether the pin it isset in accordance with awrong or right Vanswer or, as explained hereinabove, if the pin it is set at an intermediate position, the circuit willgo no further and the mark sensed bythe blades'f'l, El will not be taken into account. 'All of the blade structures 93 in any horizontal row are connected by wires 92 and through a wire |93 are connected to a blade structure 9S associatedwith the three lower pins 82 of the held identifying pins, All oi-the blade structures 92 are connected together by awire i9@ and connected by a wire 55 to the blade structured-5 which cooperates with the upper three pins .S2 at the end oi the column, that is, the sets of pins 7G are divided into ten separate groups, Y.each havingiat its outer end a set of six pins 82 (Fig` 5a). All the blade structures 92 of one set are connected to the blade structures cooperating with the upper three pins 32 and all the blade structure oi any group are connected to the blade structures cooperating withtlie three lower pins S2. Y

En the circuit diagram Fig. 5a, only a few -of the pins are shown to avoid needless repetition oi Eike parts. The pins 82 serve to connect the circuits from the related Vset of pins i6 to any of the three formula switches through'a selected pair of related wires 97. Y

For example, if the main key sheet is periorated in the position opposite the A-Wrone pin $2, this pin will be shifted to make connection with the blade structure S5 so that, if markis made in the related eid in a position representing a wrong response, the circuit from line i9! will go through wire 59, the sensing blades El,

54, resistor E55, pin i5, which will have beenmoved' 'of A romania Sra/itch mA. siminny, if the perforation in the iield selection position had been made in line with the B-wrong pin 82,

the same circuit would connect the sensing blades through the B-wrong wire |91 tothe blade Fl of the B iormula switch i833. In this manner the` circuit through any marking position on the reN spense sheet, if it represents a correct answer,

will follow rst to one vofi the blade `vstructures 93 and thence according to the setting in the lower Vthree pins 182 and the related section of the key .sheet will be directed to any one of the three formula switches. Ifany marking represents an incorrect answer, the related sensing blade-will be connected through the blade structure 92 to vany of thethree formula switches according to the positioning of the upper three pins 82 Vci the related setof pins. Y Y

When the A formula switch is in the dottedline position shown in Fig. 5 with Yblade F2 contacting the R segment EZa, the fA rightf wire IS7 isconnected through wire 2nd@ to an inter'- mediate point on the resistance 2&5, thus comthe rst of the contacts Stili closes toconnecty the upper-most resistor (tei in the other branch of the bridge, this branch Ybeingtraceable from the connecting point 3%, wire 35i, upper-most resistor 365, wire 368, wire 36.9 to negativeside of battery. At the same time', contacts 352 close under control ci cam .3451. This closure is ineffective, however, for the following reason.

n series with the contacts are the Vcontacts Ria of a high speed relay magnet Rl whichgis in series with contacts 35i and the plate of a thyratronv tube 3H. The grid ci this tube is wiredrto the secondary coil Sie of an impulse transformer whose primary coil is 363. The grid of the tube is negatively biased through connection from the negative side ci ybattery mi, through wire yariableresistor 35, coil il to the grid. The contacts S open to breakthe circuit from the primary winding to the impulse transformer. Upon such breaking a transient is transmitted from the primary of contacts Ria. Immediately thereafter, contacts,k

Y 352 close. Since the high Vspeed relay has opened the circuit, no current will now through the l print magnet 33E. ImmediatelyT after this, Vcontaots 35| open theanode circuit` oi' the thyratron tube,'thus deionizing the. tube preparatory to the next amount represepe'ntin.fr condition of the printing mechanism. AThis action takes place each time the print wheels advance one digit to introduce an additional resistor SSE in the arm of` the bridge. f

When four resistors have been introduced which are the equivalent of the four resisto-rs 59 introducedin the other arm, the voltage across the primary of the impulse transformer isrzero. At this point breaking of the primary impulse transformer contact 3dS does not cause the transient to be impressed upon the rid of the thyratron. Hence, the thyratrondoes not ionize and the high speed relay magnet Rl is not energized so that its contacts remain closed when contacts 352fclose, and a circuit is now completed through the print magnet 33d` which is traceable from negative side of battery, wire SES, resistancel 85, magnet 338, contacts 352 and Ria back topositive sideof battery.` l

, Y'Ihe energization oi the magnet 338 at this time means coordinated with said Wheels forv adjusting the resistance of a fourth armof said bridge as the y.successive numbers are registered to set up resistance values of all the numbers 1 to 99 in succession, and means controlled by theV bridge upon reaching equilibrium for rendering the irnpression Vtaking means effective to print from the Wheels-at the time said equilibrium is effected,

said setup resistance values returningto zero at the time the :Wheels return to zero.

6. In a printing machine, a Wheatstone bridge having two Varms of predetermined ohmic value, record controlled means for adjusting the resistance of a third arm of said bridge, printing type elements positionable to representv any amount, means coordinated therewith for adjusting the resistance of a fourth arm of the bridge in accordance with the amount represented byY the type elements, an induction transformer having its primary coil conductively connected in the diagonal of the bridge, a printingcontrol magnet, energizing means therefor, a thyratron tube having its grid connected With the second ary coil of said transformer, and means controlled by the tube for rendering said energizing means ineffective While the bridge is unbalanced and rendering the same effective when the bridge is in equilibrium.

7. In a printing'machine, means for sensing a record sheet for marks thereon, a plurality of resistors of Vlike ohmic Value, means controlled by said sensing means -for connecting a number of said resistors in parallel inaccordance with the number of marks sensed, a printing Wheel positionable to represent an amount, a second plurality of resistors connectable in parallel in accordance Wtih the value of the amount positioned on said wheel, hammer mechanism, a magnet for causing said mechanism to print from said Wheel, comparing means including a Wheatstone bridge arrangement for determining the relationship between the number of marks sensed and the amount standing on the 4printing Wheel, and means controlled thereby for causing energization of said magnet when said compared amounts are alike. Y

8. The invention set forth in claim 7 in which automatically operating vmeans is provided to advance said Wheel through various amount representing positions, and means for automatically rendering said comparing means operative after each amount representing positioning of the wheel whereby the actuating magnet will be tripped upon the positioning of the Wheel in correspondence with the number of marks sensed.

' REYNOLD B. JOHNSON. 

